1. Field of the Invention
The present invention relates to a portable videophone unit which is provided with a display and a camera and which is capable of conducting videophone communications by sending and receiving image data and sound data.
2. Description of Related Art
In recent years, there have been videophone units which are provided with a camera and a display and which conduct so-called videophone communications by sending sound data and image data obtained by the camera to an opposite unit, and receiving sound data and image data sent from the opposite unit, and by outputting the sound from a speaker and displaying the image in a display.
The following problems occur when such units are made portable.
Conventionally, even in so-called portable phones or PHS phones used to transmit only sound data, there were cases in which disturbances occurred in data transmission between a unit and an opposite unit for a variety of reasons, such as base station crowding (traffic), handovers occurring during the switching of base stations which accompanied the movement of the users, weak electrical fields produced when the radio situation between a unit and its base station was poor, and the like.
In such cases, conventional portable telephone units which transmitted only sound data simply experienced interruptions in the sound; however, when portable videophone units such as those described above are employed, when videophone communications are conducted, when the transmission of image data cannot be conducted well for the reasons described above, there are problems such as incomplete images which are displayed in the display.
In response to this, methods which exist for data transfer which are capable of correcting the data when an error is caused in the transmission of image data are, for example, those termed the FEC method and the ARQ method and the like (details thereof will be given hereinbelow).
However, even when the data are corrected using these methods, images are transmitted in order at fixed intervals by portable videophone units, so that until the image is switched, if the data of the image which is to be subsequently displayed cannot be corrected, it becomes impossible to display the subsequent image in the display, and from the perspective of the user, the images displayed in the display will appear unnatural.
The present invention was created in view of the points described above, and has as an object thereof to provide a portable videophone unit which is capable of displaying images in the display without an unnatural feeling, even when the transmission of image data is not conducted satisfactorily.
A first aspect of the present invention is a portable videophone unit having a data transmitting-receiving section which transmits and receives image data and sound data to and from an opposite unit, which is provided with a display which at least displays images obtained by decoding image data transmitted from the opposite unit, and a control unit which controls the images displayed in the display; the structure is such that image data of a plurality of images are successively transmitted in amounts of one image at a time, and in the control unit, after it is confirmed that all the image data of the image to be displayed have been received, the image obtained by decoding this image data is displayed in the display.
In this way, an image is displayed in the display after all the image data are complete, so that it is possible to display a complete image in the display.
In a second aspect of the present invention, in the portable videophone unit of the first aspect described above, in order to confirm that all the image data of the image have been received, an end signal contained in the frame end of the image data is detected.
In a third aspect of the present invention, in the portable videophone unit of the first or second aspect, the image displayed in the display continues to be displayed until it is confirmed that all the image data of the image have been received.
By continuing to display the previous image until it is confirmed that all the image data have been received, there is no interruption in the image displayed in the display. At this time, at predetermined intervals, the image displayed in the display may be temporarily erased and redisplayed.
In a fourth aspect of the present invention, in the portable videophone unit of one of the first through third aspects, when it is impossible to confirm the receipt of all the image data of the image, the image data of the image are discarded, and the decoding of the image data of a subsequent image is initiated.
By means of this, when the receipt of all the image data cannot be confirmed within a preset time period, or when confirmation is impossible even after generating a predetermined number of data retransmission requests in the ARQ method, it is possible to discard the image data of that image and to display the subsequent image.
In a fifth aspect of the present invention, in the portable videophone unit of one of the first through fourth aspects, the plurality of images transmitted in succession from the opposite unit are images obtained at predetermined intervals by the image acquisition section provided in the opposite unit.
Images obtained at predetermined intervals in the opposite unit are transmitted in succession, so that still images are displayed in succession at predetermined intervals in the display.
In a sixth aspect of the present invention, in the portable videophone unit of one of the first through fifth aspects, when the receipt of the all of the image data of the image cannot be confirmed, the image data of the image are corrected by the correction section.
When the image data are not complete, the image data are corrected by a correction section using the ARQ method or the FEC method or the like, and it is possible to display an image at the point in time at which the image data are completed.
In a seventh aspect of the present invention, in the portable videophone unit of one of the first through sixth aspects, when image data and character data are transmitted from the opposite unit, the data correction is conducted by the ARQ method.
When image data and character data are transmitted, in other words in the case of mail with an attached image, by correcting the image data where necessary using the ARQ method, it is possible to reliably display the image and the series of characters without gaps in the data.
In an eighth aspect of the present invention, in the portable videophone unit of one of the first through seventh aspects, the sound data transmitted from the opposite unit are corrected using the FEC method.
The frame unit when sound data are transmitted and received is, for example, approximately 30 ms, so that transmission of the sound data is conducted at high speed, and it is possible to prevent interruptions and the like in the sound.
In a ninth aspect of the present invention, in the portable videophone unit of one of the first through eighth aspects, after a first image is displayed in the display, the image data of another image subsequently transmitted are differential data with respect to the image data of the immediately previous image.
By means of this, it is possible to apply the composition described above to the so-called frame differential method as well.